Businessmen Felix Gane and John Leval require a ruthless associate to help them take advantage of slave labour in the Congo rubber industry George Marsden Plummer who overhears their plans while burgling Ganes house introduces himself and is duly judged to be the man for the job He arrives in the Congo accompanied by three roughnecks Sam Mitt Pete Carron and Nick Jute and immediately wrests control of the rubber plantation from its kindhearted manager Will Mann Realising that hes at the mercy of criminals Mann escapes into the jungle but is recaptured wounded and imprisoned Managing to pass a letter to his faithful servant Jim he sends the man away to travel to England for help Weeks later Jims journey ends at Baker Street and Sexton Blake takes up the case